Positive margins after mastectomy in patients with invasive lobular carcinoma of the breast: Incidence and management strategies.

Background: Surgical treatment of invasive lobular carcinoma (ILC) is challenging due to its diffuse growth pattern, and the positive margin rate after mastectomy is poorly described.

Methods: We retrospectively determined the positive margin rate in those with stage I-III ILC undergoing mastectomy. We evaluated the relationship between management strategy and recurrence free survival (RFS).

Results: In 357 patients, the positive margin rate was 10.6% overall and 18.7% in those with T3 tumors. Having a positive margin was associated with significantly shorter RFS on multivariate analysis (p = 0.01). Undergoing additional local treatment (radiation or re-excision) for a positive margin was significantly associated with improved RFS (p = 0.004). Older women with positive margins were significantly less likely to undergo additional local therapy.

Conclusions: Even mastectomy fails to clear margins in a high proportion of patients with large ILC tumors, a finding which may warrant testing neoadjuvant strategies even prior to planned mastectomy.